Interesting subject. Here in Wisconsin both trucks and trailers cost me the same based on ratings. It appears similar to what is done in Indiana? I have my F650 truck registrated at 26K (GVWR is 26,000) and a GN trailer rated at 22K but registered at 26K (only options are 20K or 26K). The truck has a GCWR rating of 42K even though if you added the combined trailer & truck loads it would be higher from a registration standpoint. Never had a problem when checked but typically don't pull more than 20K and together with truck my GCWR weight is around 33K. When it comes to GCWR I believe it is figured based on the actual weight of the truck/load plus trailer/load and not the manufactuer vehicle GVWR.